The present invention relates to detector systems, particularly to the detection of extremely low concentrations of emissions or airborne compounds, and more particularly to an ultra sensitive detector for hand-held gas chromatographic analyses of various gases or compounds while being insensitive to other materials.
Emissions generated during manufacturing operations, such as the manufacture of weapons of mass destruction, are generally at extremely low concentrations downwind of any manufacturing facility. In order to support field collections and analysis of such target species in a complex matrix, very sensitive and highly specific analytical tools are required.
Recently, a hand-held (portable) gas chromatographic oven and pancake capillary gas chromatographic column has been developed at the Lawrence Livermore National Laboratory for fast gas chromatographic analysis of industrial gases. However, in order to support field collections and analyses using implace sensors, a new type detector for use in conjunction with gas chromatography, which is both highly specific and extremely sensitive, is needed.
The present invention provides such a ultra-sensitive detector for hand-held gas chromatographic analyses of high explosives (HE), chemical weapons (CW), CW-precursor and CW-hydrolysis compounds, hydrogen (tritium), and other organic compounds, in particular biochemicals biological weapons (BW), signature, for example, while being insensitive to H2O, N2, He, Ar, O2, CO2, and saturated hydrocarbon gases. The key detector of this invention utilizes gas phase redox reactions and spectral absorption of atomic mercury (Hg). Compounds easily oxided by mercuric oxide (HgO) with liberate atomic mercury that subsequently passes through a quartz cell, illuminated with 254 nm ultra-violet (UV) light. Utilizing mercury as the indicator species, this detector is exquisitely sensitive (low femtograms) to target compounds of interest.
It is an object of the present invention to provide an ultra-sensitive detector for field collection and analysis of manufacture emissions, airborne compounds, etc., collected on a suitable matrix.
A further object of the invention is to provide an ultratrace detector for hand-held gas chromatography of various organo- and organo-metallic compounds, gases, etc.
A further object of the invention is to provide a detector system that is both specific and extremely sensitive.
Another object of the invention is to provide an ultra-sensitive detector arrangement in combination with a hand-held gas chromatograph.
Another object of the invention is to provide a detection and analysis system using a gas chromatograph in combination with a heated redox-chamber, a detection chamber, and a vapor trap.
Another object of the invention is to provide a detector in combination with a capillary gas chromatograph (GC), wherein the GC initially separates compounds that percolate through a bed of heated mercuric oxide in a silica-aerogel material, which liberates atomic mercury that is passed through an ultra-violet detector cell for identification, and thereafter is collected in a vapor trap.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The invention involves an ultratrace detector for hand-held gas chromatography of target species, such as high explosives, hydrogen gas, biological compounds, drugs, etc. The invention enables detection limits that can approach or exceed femtogram levels for unique compounds in complex mixtures, yet be insensitive to non-reactive compounds such as water, helium, argon, oxygen, carbon dioxide, and saturated hydrocarbon compounds. The invention provides a gas chromatograph/detector system that is small, specific, and extremely sensitive. The detector uses gas phase redox reactions and spectral absorption of liberated mercury vapor. The redox reactions are carried out in a bed of heated mercuric oxide (HgO) in a silica, other mineral bed, or aerogel material which provides insulation for the bed. Compounds oxidized by HgO will liberate atomic mercury that passes through a detector-cell illuminated by a mercury discharge lamp. The liberated mercury atoms are then collected in a small Hg vapor trap. The mercury vapor trap can be used as a detector when properly recharged in a laboratory.